Abstract In this K99/R00 Pathway to Independence award application, Dr. Kyle McCommis outlines detailed plans to enhance his research training in state-of-the-art cardiovascular metabolism techniques while simultaneously addressing a novel mechanism to altered metabolism during various cardiomyopathies. Dr. McCommis is currently a postdoctoral research scholar at the Washington University School of Medicine, and has a strong background in assessing cardiac function, and the role of mitochondria in cardioprotection. Kyle?s recent research training delved into hepatic and ?-cell mitochondrial pyruvate metabolism. Herein, he seeks to marry these two areas of research expertise to investigate the importance of mitochondrial pyruvate metabolism in the heart. A primary goal of Dr. McCommis is to become an independent investigator in cardiometabolic research, thus a career development plan has been proposed in which he will train with experts in various aspects of cardiac metabolism (Drs. Finck, Lewandowski, and Schaffer). From Dr. Lewandowski he will learn: (1) the isolated perfused mouse heart preparation, (2) expand upon Kyle?s experience using tracers to understand metabolic pathways, and (3) NMR analysis of tracer metabolite flux. From Drs. Finck and Schaffer, Kyle will learn: (1) the molecular and cellular alterations that occur in diabetic hearts, (2) the nuances of running a research laboratory, and (3) guidance on initiating and developing an independent research career. Collaborators have also been identified to instruct Kyle on the isolation of primary adult cardiomyocytes as well as provide assistance with performing and interpreting metabolomic analyses. Metabolism of pyruvate is essential for the working heart which requires large amounts of ATP to fuel contraction. During cardiac ischemia, hypertrophy, or diabetes, pyruvate metabolism is significantly diminished. However, the mechanisms of these metabolic alterations are far from understood. Regulation of the activity of the newly identified mitochondrial pyruvate carrier (MPC) likely plays a role in these adaptations. However, nothing is known regarding the regulation of the MPC in the heart or how pathogenic conditions associated with impaired pyruvate utilization affects MPC activity. The goals of this work are to: (1) determine the acetylation status and activity of the MPC complex during ischemia, hypertrophy, and diabetic cardiomyopathy, (2) identify the deacetylase responsible for modifying MPC proteins, (3) identify the acetylated lysine residue(s) of MPC2, (4) phenotypically characterize the cardiac function and metabolism of cardiac-specific MPC2-null (CS-MPC2-/-) mice, and (5) analyze the response of CS-MPC2-/- mice to diabetes, hypertrophy, and ischemia. The overarching goal of this proposal is to develop Dr. McCommis into a productive independent investigator. The knowledge and experience obtained from the proposed research and career development plans will provide him the boost he needs to become a fruitful independent investigator and secure R01-type funding.